1. Field of the Invention
This invention relates to a head lamp a vehicle and more particularly to a constitution which further can be improved to the head lamp of type constituted by combining a reflecting surface, a shield plate, a elliptic system projection lens or the like such as spheroidal reflecting surface and referred to as a projector type, and the object of the invention is to provide the constitution of the head lamp for the vehicle.
2. Detailed Description of the Prior Art
FIG. 10 shows an example of a constitution of a prior projector type head lamp 90, and a light source 92 is arranged at a position of a primary focus f1 of an elliptic system reflecting surface 91 such as a spheroidal reflecting surface of which major axis is aligned with an illuminating direction X. Moreover, a shield plate 93 is provided at the vicinity of a position of a secondary focus f2, which shields the approximate half of the lower of luminous flux converged into the secondary focus f2 from said elliptic system reflecting surface 91.
According to this constitution described above, since a cross-section shape of luminous flux in the vicinity of said shield plate 93 becomes a approximately half-round shape of last quarter, this shape is projected in the illuminating direction in the condition which becomes a half-round shape of first quarter that the upper and the lower are reversed when projecting this shape in the illuminating direction by a projection lens 94 having a focus f3 at the vicinity of the shield plate 93.
Therefore, it can be obtained a light-distribution pattern optimal for a passing beam including perfectly no upward light which becomes a factor by which the glare is caused to an on-coming vehicle. However, modification is given on the shape of the shield plate 93 so as to produce the appropriate upward light on the left side when being supposed to pass in the left side in order to facilitate to recognize pedestrians or road signs on the side of a roadside at the occasion of an embodiment in practice.
However, there has been a problem that in the head lamp 90 with the prior constitution, the approximate half of the reflected light from the elliptic system reflecting surface 91 is shielded by the shield plate 93 as is apparent from description described above, as a result, an utilization factor of luminous flux with respect to a light source 92 is reduced and the head lamp becomes poor in intensity for power consumption. Moreover, the light emitted to the front side (the illuminating direction) from the light source 92, which can not reach the elliptic system reflecting surface, does not contribute formation of a light-distribution characteristic and the utilization factor of luminous flux also is reduced in this point.
The present invention can solve the problems by providing a head lamp for a vehicle as specified means for solving the prior problems described above, wherein a first elliptic system reflecting surface_having an optical axis in the illuminating direction of the head lamp and arranging a primary focus on the light source and a second elliptic system reflecting surface arranging the primary focus on the same light source and intersecting the optical axis at approximately right angle to the optical axis of said first elliptic system reflecting surface are provided, the projection lens, corresponding to the secondary focus of said first elliptic system reflecting surface and the shield plate, as required are provided, and a parabolic system reflecting surface approximately taking the secondary focus as a focus, corresponding to the secondary focus of said second elliptic system reflecting surface and the shield plate and approximately taking the optical axis as the illuminating direction is provided.